Many conventional tie-rod designs for hydraulic hammers use a flat contact face requiring the machining of a sizable spot-face on the component being held. The precise flatness and perpendicularity of the spot-face of the spot face affects the integrity of the bolted joint. Angular misalignment of the tie rod may result if the spot face is not properly machined.
Conventional tie rod designs may be expensive to manufacture due to the much larger diameter of the torque end, and more particularly the flange. For example, a machined tie-rod requires a much larger diameter bar stock from which a large percentage of the material is removed attributing to higher cost. Also, the large spot face or flange requirement often show up as a difficult feature for 3D printing because the feature an over-hang requiring underlying support. The support material as well as the base must be removed after printing and in the case of metal parts, the support material must be machined away, adding cost.
U.S. Pat. No. 4,137,816 discloses an expansion dowel that is introduced into a borehole and that has a sleeve, an expanding body to be displaced into the sleeve for expanding it, a tie rod that is connected to the expanding body and an end support on the tie rod for applying torque to the dowel assembly. Torque is applied to the working surfaces on an end support of the dowel, that is, a bolt head or a nut, and the tie rod pulls the expanding body into the sleeve, spreading the sleeve into anchoring contact with the surface of the borehole. The expanding body may have a frusto-conically shaped surface that engages the sleeve and spreads the sleeve apart, creating a connection between the upper and lower ends of the expansion dowel. This connection relies solely on friction to maintain the holding power of the connection.
Accordingly, it is desirable to develop an improved tie bar connection for a hydraulic hammer and the like that is easier to manufacture and that provides a more robust connection than has been previously devised.